Alexander Arrow, analyst for Lazard Capital Markets, estimates that sales of Allergan's Juvederm franchise will overtake Medicis' Restylane franchise as the leader of the dermal filler industry this year.

Arrow estimates that Juvederm and other dermal filler products from California-based Allergan will take 41 percent of the market share in 2007, up from 28 percent in 2006, usurping Medicis' role as industry leader. Arrow projects that Medicis' dermal filler franchise, including Restylane and Perlane, will slip from its 2006 level of 51 percent, to 36 percent in 2007.

Another analyst, Corey Davis of Natixis Bleichroeder, believes that Arizona-based Medicis will remain the market leader this year but by a mere $7 million. Davis projects 2007 sales of $140 million for the Restylane franchise versus $133 million for the Juvederm products.

Medicis chief executive Jonah Shacknai did not provide sales estimates for Restylane, which entered the U.S. market in 2003, but denied that's its industry leadership was being threatened.

"Restylane is experiencing significant growth," said Shacknai to CNNMoney.com. "We maintain overwhelming leadership in the dermal filler marketplace in the U.S. and the world."

Allergan spokesperson Caroline Van Hove said sales of Juvederm, which entered the U.S. market in 2006, were fast-growing, but she didn't break out the numbers for specific products.

Dermal fillers are used to smooth wrinkles by injecting fillers made from various ingredients into the face. The effects generally wear off after about six months, requiring fresh injections. Competing products often last for different durations.

In July, the Food and Drug Administration approved Allergan's Juvederm to last for a year, from its prior duration of six months. Medicis' Restylane is approved to last "at least" six months, according to the company.

Meanwhile, competitor Artes Medical is breaking into the market with its product ArteFill, which is FDA-approved to last one year but theoretically lasts forever.

"The duration is one of the key factors that doctors decide on when choosing a brand of dermal filler," said Arrow of Lazard. "Artes Medical has a unique advantage because it has a permanent dermal filler. Theoretically, it would last a lifetime."

Artes Medical, a San Diego company that went public in 2006, launched its permanent dermal filler ArteFill this year. ArteFill contains polymer microspheres that remain in the face long after its supporting gel fades away - supposedly forever.

But some analysts believe that doctors and patients might be afraid of a facial injection that's considered permanent. More people are seeking eternal youth, but just for a few months at a time, analysts say.

"There are some doctors who won't use ArteFill because they're afraid that any mistakes they have are permanent, and some patients feel that way, as well," said Arrow of Lazard. "That's why we think ArteFill will never become a market leader."

Arrow estimates that the newly-launched ArteFill will total $13 million in 2007, barely trailing competitor BioForm's Radiesse, which is expected to total $15 million.

Nonetheless, Artes Medical said that 800 physicians have opened accounts to use ArteFill, and 600 of those doctors have completed training to use the new product, a promising sign that product sales could grow in the near future.

"The company trained over 600 physicians on the ArteFill procedure by July and is on track to train close to 1,000 by year end - well ahead of our previous expectations," wrote Sara Michelmore, analyst for Cowen and Co., in a note published Aug. 10.

But Aaron Gal, analyst for Sanford C. Bernstein, said "the question is not how many doctors will sign on, but how many doctors will use your product, and how often. [ArteFill is] a permanent filler and doctors are afraid of committing to use this. Permanent use means permanent problems."

This might be partly responsible for Artes Medical's 40 percent plunge in stock so far this year, though Arrow of Lazard said much of the decline comes from a stock lockup that was lifted six months after the IPO.

Jose Haresco, analyst for Merriman Curhan Ford, said in a published note that Artes Medical might be getting squeezed by BioForm Medical, a privately-held California company that recently filed for an IPO.

BioForm's dermal filler Radiesse, which was approved by the FDA in 2006, lasts for a year "on average," according to the company. BioForm licenses the technology to make its product from competitor Artes Medical.

Gal of Bernstein said that ArteFill might eventually pay off, but it will take a while.

"[Artes Medical] has got a long road ahead of them to prove its product is good," said Gal. "It's a competitive marketplace and they make a difficult proposition for a doctor to accept a permanent product. It's not going to be a walk in the park. But in the long run, if their product is good and has no side effects, then doctors will use it and the company will succeed."